Solvent recovery in combined solvent refining process



P 20, 1966 J. D. BUSHNELL ETAL 3,274,096

SOLVENT RECOVERY IN COMBINED SOLVENT REFINING PROCESS Filed Sept. 27, 1962 2 Sheets-Sheet 1 VLESE DEASPHALTEDOIL PROPANE Z A125 FEED 3 7 VAPORIZED FLASH PROPANE p.42 9 DRUM FIG. l

DEASPHALTING TOWER '3 PROPANE I24 HEATER 4 E 6 K LVAPORZEO PROPANE ,6 AsPHALT-PROPANE PROPANE 8 COMPRESSORI29 [3O 7 3 J1 7 {ASPHALT O T Pvt 1"??? 68 65 -|3| 2 FLASH I23 DRUM a? IGER %Y Q PHENOL l 7 FLASH -PREFIANE DRUM v ORS 5-2 WAX \IZI '\6O 7| OUT -I3O FILTER 72 -PROPANE FEED M PROPANE E E VAPORS I26 134, r M PROPANE CHILLER CHILLER CONDENSER LlQUlD ,59 ,59A PROPANt \l 53 |32 55 A 54 MIXER\ 58- 56 T T 55 HOLD-UP VDRUM 52A 52 5I| 57 SOLB'A'AION/ DEASPHALTED DR JAMES D. BUSHNELL JOHN L. EHRLER INVENTORS HAROLD N. WEINBERG BY M Ma PATENT ATTORNEY Sept. 20, 1966 J. D. BUSHNELL ETAL Filed Sept. 27, 1962 2 Sheets-Sheet 2 HOT PHENOL E3 VAPOR l FURNACE RAFFINATE PHASE, 35

OIL+PHENOL\ W T FlG.-2 24 -e I03 '3 IO! E uoum PHENOL /3s PHENOL STORAGE PHENOL "/22 VAPOR PHENOLTREATING 2| TOWER 83 EXTRACT PHASE, T 39 ARoMAT|Cs+ FEED PHENOL 23 PHENOLRAFFINATE 82 RECOVERY M 381A TOWER V 1 FURNACE w TO DEWAXING 37 STEP 26 HOT 27 PHENOL PHENOL 25 TRACT RECOVERY TOWER 28 33 32 DEAROMATIZED f o|| RECYCLE 29 STRIPPING GAS BSA AROMATICS lea ASPHALT-PROPANE E-! E-3 E-5 E-4 23 24 e 66 3 E E 99 I00 98 JAMES C. BUSHNELL |0| JOHN L. EHRLER INVENTORS Z HAROLD N. WEINBERG BY f (33:3 J

PATENT ATTORNEY United States Patent 3,274,096 SOLVENT RECOVERY IN COMBINED SOLVENT REFINING PROCESS James D. Bushnell, Berkeley Heights, John L. Ehrler, Landing, and Harold N. Weinberg, East Brunswick, N.J., assignors to Esso Research and Engineering Company, a corporation of Delaware Filed Sept. 27, 1962, Ser. No. 227,123 2 Claims. (Cl. 208-34) The present invention relates to an improved apparatus and process for producing lubricating oils. It is concerned with combining the process steps of deasphalting, solvent extraction and dewaxing, and relates particularly to the recovery of the solvents utilized in the various process steps. Specifically, it concerns improvements in the recovery of the solvent from the rafiinate and extract phases obtained from a solvent extraction treatment, and to the recovery of the deasphaltin-g and dewaxing solvent. Mor specifically, the invention relates to an efiicient heat transfer between hot solvent vapor distilled from the extract and rafiinate fractions, from the solvent extraction process, and the relatively cool process streams from the deasphalting and dewaxing steps. The hot extraction solvent vapors are indirectly heat exchanged with the rela tively cool deasphalting and dewaxing process streams to vaporize the solvent from the deasphalting and dewaxing streams. Simultaneously, the hot extraction solvent vapors are cooled and condensed.

In lubricating oil refining processes, one of the conventional steps is to selectively extract aromatic hydrocarbons from the lubricating oil by using a solvent which preferentially dissolves aromatics. An example of a suitable solvent is phenol. The phenol is countercurrently contacted with the feed and separates into two phases: a solvent extract phase rich in aromatics and an oil raflinate phase with most of the aromatics removed. The phenol solvent is subsequently recovered from raffinate and extract phases by high temperature distillation.

Heretofore, a large amount of cooling capacity was required to condense the hot phenol vapors from the phenol solvent recovery step. This has resulted in the waste of the heat energy available in the hot phenol vapors, as well as necessitating substantial investment for cooling water and cooling apparatus.

In the dewaxing and deasphalting plants, most of the dewaxing and deasphalting solvent is recovered by vaporization wherein steam is used as the source of heat.

In accordance with the present invention, the process steps of deasphalting, phenol treating, and dewaxing, are closely integrated by the combination of all the deasphalting and dewaxing solvent recovery systems, and by a phenol hot belt system which transfers the heat from the phenol solvent vapors to the process streams of the deasphalting and dewaxing steps, wherein the solvent is vaporized from the latter streams while simultaneously condensing the hot phenol vapors.

To insure adequate heat in the phenol hot belt during periods of low phenol circulation rate in the phenol plant, phenol solvent can be injected into the extract stream prior to its entry into the phenol extract furance.

Another aspect of this invention is the use of a furnace recycle system whereby hot extract solution from the extract recovery furnace provides heat for the recovery of solvent from asphalt separated in the deasphalting unit. The recovery of solvent from asphalt must be carried out at high temperature to reduce the viscosity of the asphalt solution to prevent foam carryover. Since these temperatures are not generally attainable with steam, a separate furnace has been required in past practice. The

use of an extract furnace recycle stream obviates the need for a separate furnace.

Further, before heat exchange with the furnace recycle stream, the asphalt solution is preheated by the bottoms from the extract recovery tower. The bottoms from this tower contain the most heat energy when the yield of extract is high; at these times, the extract furnace is at maximum duty and has less available heat for the asphalt solution. Thus, the use of the two exchangers is a balancing factor.

In accordance with this invention, the heat energy available in the hot phenol vapors is utilized to heat the process streams from the deasphalting and dewaxing steps to a temperature at which the solvent can (be removed from these streams while simultaneouly cooling the hot phenol vapors.

Further, in accordance with this invention, the process steps used to produce refined lubricating oil blending stocks have been integrated into a compact processing plant. The processes are interrelated to obtain maximum process advantage and use of available heat energy and cooling capacity.

Briefly, an integrated lubricating oil plant comprises in combination the following process steps: A solvent deasphalting step in which undesirable asphaltic materials are precipitated and deasphalted oil recovered. After deasphalting, the deasphalted oil is solvent extracted with a solvent which is selective to remove the aromatic components. The removal of aromatic components improves the viscosity index, color, and stability of the refined oil.

The solvent-refined, deasphalted oil is then subjected to a solvent dewaxing step wherein paraffinic Waxy material is removed and the pour point of the resulting product reduced. Some of the refined oils can be obtained from a low pour point naphthenic crude; these particular stocks may bypass the dewaxing step.

The principal integrating features of the plant are in combining the solvent recovery systems for the deasphalting and dewaxing process steps and in the heat exchange step between the recovered vapors of the selective solvent and the relatively cool deasphalting and dewaxing solvent-bearing streams.

The present design is flexible enough to handle a complex slate of operations and the design principles are applicable to a broad range of different processing steps. Various lubricating oil fractions may be fed to the above described plant wherein each fraction undergoes one or more of the above process steps in whatever combination is required to obtain a refined lubricating stock having the desired properties of viscosity index, pour point, odor, color stability, etc.

There are two basic types of crude oil employed in lube manufacturing. They are paraifinic and naphthenic crudes. Naphthenic crudes generally do not require dewaxing; suitable low viscosity index (VI) lube stocks may be made simply by hydrofining a selected fraction, or moderate VI stocks may be manufactured by extracting and hydrofining naphthenic distillates. With paraffinic crudes, however, dewaxing is required to obtain the desired pour point. Depending on the properties desired in the lubricating blending stocks, suitable feeds ranging from 600 F. IBP gas oil fractions to vacuum residual fractions are used which can undergo one or more of the above described process steps.

In order to better understand applicants invention, a brief description of the various process steps and how they are interrelated will be given:

Deasphalting The deasphalting process effects a physical separation of very high boiling, viscous lube oils at low temperatures, thus eliminating any thermal cracking which would take place at temperatures high enough to separate the materials by distillation. For example, an asphalt'containing residuum is contacted with about 2 to 12 volumes of liquid solvent at about 100 to 250 F. The crude residuum and the deasphalting solvent are countercurrently contacted. The overhead phase contains the deasphalted oil and most of the solvent. The asphaltic phase is removed as bottoms and contains a minor portion of the solvent. With a typical feed, deasphalting is carried out at about 250600 p.s.i.g. The overhead phase will comprise about 2090% of the feed and the rejected bottoms phase will comprise the remainder. The solvent present in the overhead and bottoms fractions is removed by separatedly heating these fractions and flashing the solvents.

Phenol treating A suitable feed, either from the deasphalting step or from another source, such as a vacuum pipestill sidestream, is countercurrently contacted with a solvent, such as phenol, which preferentially dissolves aromatic components. The removal of aromatic components raises the viscosity index and improves oxidation stability and color of the refined oil. The aromatic-rich extract phase will comprise about 1075% of the feed, depending upon the quality desired and the crude source employed. The raflinate phase contains about 2595% of the feed. The majority of the solvent leaves the treating tower with the extract phase, which will consist of about 5095% by volume of solvent. The raffinate phase contains about 4-25% by volume of the solvent. The solvent treating tower is operated at a temperature of about 100 to 250 F. and a pressure of about to 400 p.s.i.g. The pressure must be sufficient to suppress vaporization in the treating tower and convey the extract and raffinate phases to the recovery sections, either with or without pumps.

The solvent is recovered from the extract and rafiinate phases by distillation. The hot solvent vapors are combinedand subsequently used to heat the deasphalting and dewaxing process streams. Simultaneously, the hot phenol vapors are cooled and condensed.

Dewaxing Hot waxy oil feed, at a temperature above its pour point, from any of the previously discussed process steps or other suitable sources is mixed under pressure continuously with a suitable dewaxing solvent such as propane at dilution ratios in the range of about 1/1 to 7/1 of solvent to feed. A small quantity of dewaxing aid (crystal modifier such as Paraflow) may be added to the solvent/ feed solution. The mixture is then heated to dissolve any wax crystals present. The mixture is then cooled to about 80 F. and sent to the warm solution drum. The solution is then sent to either of two chillers in which the solution is cooled by autorefrigeration of the solvent. During the chilling, wax crystallizes out of solution.

The operation is arranged so that while one chiller is chilling, the other chiller is being emptied of cold slurry and filled for its next chilling operation. The filter feed drum receives the chilled batches from the chiller from which it continuously feeds one or more filters or centrifuges. The temperature, at which the solution is dewaxed, is about 0 to -40 F. The percentage of feed removed as slack wax is about 2 to 50 while the yield of dewaxed oil is about 50-98% based on feed. The wax and the dewaxed oil solutions are separately heated to recover solvent.

Solvent recovery for the deasphalting and dewaxing plants is combined. The slack wax solution, the dewaxed oil solution, and the deasphalted oil solution each exchange heat with the hot extraction solvent vapors recovered from the raffinate and extract solutions of the solvent extraction step. The dewaxing and deasphalting solvent is flashed and removed from the respective process streams.

The asphaltic solvent mixture from the deasphalting step is heated by a novel extraction solvent pumparound stream wherein the extract solution is cycled between the extract solution furnace and indirectly contacted with the asphalt solution and returned to the extraction solvent extract furnace.

Recovery of solvent from deaspalted oil, dewaxed oil, and slack wax solutions is carried out at a temperature of about 360 F. and at a pressure of about to 300 p.s.i.g. The solvent from the asphaltic solution is recovered at a temperature of about 400600 F. and a pressure of about 175300 p.s.i.g. The extraction solvent is separated from the extract and raffinate phases at a temperature of about 450650 F. and a pressure of about 10-100 p.s.i.g.

Hot belt heat exchange The hot belt heat exchange system provides the primary integrating feature between the various components of the integrated lube plant. The extraction solvent hot belt which hereinafter will be discussed with phenol as the extraction solvent, provides a means to heat and vaporize the deasphalting and dewaxing solvents. At the same time, the phenol vapors from the recovery towers are cooled and condensed. The heat normally supplied by steam in the solvent recovery sections of the deasphalting and dewaxing plants is now supplied by the condensing phenol hot belt. The integrated plant is sufliciently flexible so that it is not necessary for the entire phenol plant to be running at full capacity for the hot belt to operate. Only the circulation of the phenol is essential.

The various design features and integration of various process steps have resulted in a substantial overall savings in investment and operating costs. One principal saving has resulted from the integration of the solvent recovery systems and the use of the phenol hot belt. These features have allowed carrying out the described processes with the use of little or no steam for heating purposes. The solvent heating requirements are provided by the phenol hot belt. Residual phenol in the extract and raflinate recovery towers is stripped using a light hydrocarbon gas instead of the normally used steam. Cooling water requirements to condense the hot phenol vapors have been substantially reduced.

The above plant is operated on a variety of feeds and sequence of treating steps so that all of the units involved are normally on stream and in operation at least 90% of the time.

The invention is illustrated by the following drawings. The drawings have been simplified by omitting various pumps, compressors, motors, heat exchangers, etc. which do not form a part of the present invention.

FIG. 1 of the drawings is a schematic flow diagram of the deasphalting and dewaxing plants and the propane recovery system.

FIG. 2 of the drawings is a schematic flow diagram of the phenol extraction unit and phenol recovery system.

FIG. 3 of the drawings is a flow diagram illustrating the phenol hot belt and its relationship to the various heating and cooling services that are provided.

FIG. 1 will describe in detail the deasphalting and dewaxing process steps as well as the combined propane solvent recovery system. The description of the deasphalting and dewaxing plants will be of feed undergoing only these two treating steps, though it is understood that the feed may have previously undergone other treating steps, that a treating step may be interposed between deasphalting and dewaxing and that the dewaxed oil may be subjected to other treating steps.

A residuum feed, boiling in the range of about 900 F. to 1300 F. is fed through line 1 to the top of deasphalting tower 2 and is countercurrently contacted with an ascending stream of liquid propane introduced through line 134. The contacting is carried out at a temperature of about 100 'to 160 F. and at 450 to 550 p.s.i.g. In treating tower 2 the residuum is separated into an asphaltic fraction and a deasphalted oil fraction by the precipitating action of the propane on the asphaltic materials in the feed. The deasphalted oil/ propane solution is taken overhead through line 3. Hot phenol vapors in heat exchanger E4 heat the deasphalted oil to about 360 F. The heated solution is fed through line 7 to high pressure flash drum 8 and flashed at about 320 F. and 230 p.s.i.g. The flashed propane from the high pressure flash drum is removed overhead by line 125 which joins line 121. Line 121 picks up overhead flashed propane from other high pressure flash drums and is sent to main propane condenser 126.

The asphalt/propane solution is withdrawn from deasphalting tower 2 through line 4.- to asphaltic solution/ extract oil heat exchanger E-6A, then through asphaltic solution/phenol extract furnace recycle exchanger E-6 wherein it is heated to about 540 F. Then it is sent through line 5 to high pressure flash drum 6, wherein it is flashed at a pressure of about 230 p.s.i.g. A recycle stream from the phenol extract recovery tower 27 (see FIG. 2), exchanges heat with the asphaltic solution in exchanger E6 and is cycled back to the extract furnace. This vaporizes the propane, permitting it to be disengaged from the asphaltic material at a low enough asphalt viscosity to avoid carryover.

The flashed propane vapors are taken overhead by line 124 wherein they join line 121 and are conveyed to the propane condenser 126. The bottoms contain the asphaltic constituents and a small amount of propane and are sent to low pressure flash drum (not shown) to recover the small amount of propane remaining. The propane from the low pressure flash drum is also sent to the con denser 126 after being compressed. The asphaltic materials are removed from the bottom of flash drum 6 by line 10 and are subsequently taken to storage for further processing or disposal. The deasphalted oil may be sent to phenol treatment, hydrofining, or directly to the dewaxing step.

In dewaxing, the deasphalted oil is introduced through line 51 and introduced into mixer 52 wherein liquid propane is added at a pressure of about 350 p.s.i.g. The mixture of propane and feed is then introduced through line 52A to waxy solution holdup drum 53 where it is held at a temperature of about 140160 F. until all of the wax present in the feed has been dissolved. The feed is then cooled to about 80 F. and charged to the warm solution drum 54 from which it is fed alternately to two batch chillers 59 and 59A. Batches of warm solution are cooled by vaporizing some of the volatile propane solvent which is removed overhead by line 123, thereby precipitating some of the' wax. The waxy oil/propane solution is thus chilled to final temperatures in the range of to -40 F. The operation is arranged so that while one chiller is chilling, the other chiller is being emptied and filled for its chilling operation. The chilled solution then goes through line 58 to filter feed drum 60. From the feed drum, the crystallized wax, propane solvent and oil are continuously fed through line 61, 62, and 63 to wax filters 65 and 65A wherein the precipitated wax is separated from the oil/ solvent solution.

Propane vapors from the warm solution drum 54, chillers 59 and 59A, and filter feed drum 60 are throttled to about 3 to p.s.i.g. and sent through line 128 to com pressor 129.

In carrying out the chilling operation, it was found that crystallization begins in the prechilling stage and that prechilling conditions must be carefully controlled to avoid the formation of fine crystals which rapidly plug filter cloths. The addition of waxy solution holdup drum 53 to provide liquid holdup of the feed/propane solution before prechilling begins provides time for complete solution of the wax in the propane. The initial dilution ratio of solvent to feed is sufficient so that no makeup propane is required during the chilling cycle. The higher dilution ratio plus the holdup time allows solution of the wax to be accomplished at temperatures at or below about 140 F.

The chilled solution fed through line 62 and 63 is separated into wax and dewaxed oil by filters 65 and 65A. The dewaxed oil passes through the filter cloth into a rundown drum (not shown), and then to the propane recovery system. The wax deposited on the filter cloth is washed by liquid propane. The cake is removed from the filter by blowback gas supplied by line 131. The dewaxed oil solution is removed from the filters by line 66 and indirectly contacted and heat exchanged in phenol hot belt heat exchanger E-5 where its temperature is raised to about 340 F. while simultaneously cooling and condensing the hot phenol vapors.

The dewaxed oil solution then enters the bottom of high pressure flash drum 68 through line 67 where it is flashed at a pressure of about 235 p.s.i.g. The major portion of the propane in the dewaxed oil solution is removed in the high pressure flash drum. The remaining minor portion of the propane in the dewaxed oil is removed in a low pressure flash drum (not shown) operated at about 5 p.s.i.g. The dewaxed oil, free of propane, is removed through line 73 and sent to storage. The flashed propane is removed through line 123 and joins line 121 and is sent to propane condenser 126.

The slack wax/propane slurry is removed from wax filter and fed through line 69 to phenol hot belt exchanger E2 where it is indirectly heated to about 320 F. with hot phenol vapors, which are thereby cooled and partially condensed. The warmed wax solution is fed through line 70 to high pressure flash drum 71 wherein the propane is flashed at a pressure of about 235 p.s.i.g. Substantially all of the propane is removed. The slack wax is withdrawn from flash drum 71 by line 72 and can be subsequently further processed to recover the wax, cracked to make lighter products or used as fuel. The propane from the high pressure flash is removed from flash drum section 71 through line 122 and joins line 121 and is sent to propane condenser 126. The propane vapors in line 121 are condensed in condenser 126 and sent to propane accumulator drum 132.

The same compressor 1'29, condenser 1.26, storage drum 132, knockout drum (not shown) and associated piping are used for the dewaxing and deasphalting plant propane circulation systems. The propane recovery system takes vapor streams at about 3 to 5 p.s.i.g. from the low pressure flash drums (not shown), chillers 59 and 59A, the filter feed drum 60 and filters 65 and 65A sends them to propane compressor 129. In the compressor, the pressure is raised from 3 to 5 p.s.i.g. to about 230- p.s.i.g.

The compressor discharges, through line 130 to condenser 126, along with vapors from high pressure flash drums 6, 8, 68 and 71 introduced through line 121 is condensed by condenser 126 and introduced into propane accumulator storage tank 132 through line 127. Liquid propane from storage 132 is recycled through line 133 and 134 to deasphalting tower 2 and through line 135 to dewaxing propane mixer 52.

In describing FIG. 2 of the drawing, a feed which is only phenol extracted will be discussed. Feed enters the bottom of phenol treating tower 22 through line 21 and is counter-currently contacted with liquid phenol fed into the top of tower 22 through line 103. The feed is first heated to a temperature of about 200 F. by heat exchanger (not shown). A rafiinate phase is removed overhead through line 24. The extract phase is removed from the bottom of phenol treating tower 22 through line 23. The extract phase contains most of the phenol solvent and extracted aromatic hydrocarbons. The overhead raflinate stream contains a minor amount of phenol solvent and most of the nonarornatic hydrocarbon components. The phenol treating tower 22 is operated at a temperature of about 200 F. and a pressure of about 100300 p.s.i.g.

The raffinate stream is heated to about 400 F. by passage through phenol hot belt heat exchanger E-3 wherein it is indirectly contacted with hot phenol vapors. It is then fed to furnace E8 through line 35 where it is heated to about 650 to 750 F. It is then sent to raffinate phenol recovery tower 37 through line 36, wherein vaporized phenol solvent is separated from the raffinate. Phenol solvent recovery is maximized by stripping with light hydrocarbon gases introduced into raflinite recovery tower 37 through lines 31 and 32. The hot phenol vapors leave tower 37 via line 82 at a temperature of about 435 F. and a pressure of about 50 p.s.i.g. and are subsequently combined with the phenol solvent vapors from tower 27 in line 83. Line 83 leads to the phenol hot belt system. In the hot belt system, the hot phenol vapors are cooled and condensed and finally discharged into the phenol accumulator drum 102.

The raffinate, free of phenol solvent, i removed by line 38 and fed through line 39 to a rafiinate storage tank or through line 38A to a hydrofining reactor and/or a dewaxing step. The phenol extract fraction from phenol treating tower 22 is removed from the bottom of the tower through line 23 and heat exchanged in phenol hot belt exchanger E1 with hot phenol vapors. Its temperature is raised to about 400 F. and it is then sent through line 25 to extract recovery tower furnace E-7 where it is heated to about 600 F., partially vaporizing the phenol. The partially vaporized phenol and extract phase is fed through line 26 to extract recovery tower 27. Hot phenol vapors are taken overhead through line 81 where they are combined with the vapors from raffinate recovery tower 37 in line 83. Below the point where the feed is introduced, a stripping gas is introduced into extract recovery tower 27 through line 31 and 33 to strip any remaining phenol from the extract. The bottoms product is discharged at a temperature of about 500 F. from tower 27 through line 30 and consists mostly of aromatic components. This product is sent to storage after suitable heat exchange.

A portion of the phenol extract phase introduced into extract recovery tower 27 is recycled through line 28, heat exchanger E-6, and line 29 back to extract furnace E7. This extract recycle at a temperature of about 600 F. exchanges heat with the asphalt/propane solution from the deasphalting step described in FIG. 2, heating that stream to a temperature of about 540 F. Additional heat energy is obtained by heat exchange of the asphalt/propane solution with the extract bottoms in line 30 in heat exchanger E-6A.

Cool condensed phenol vapors from the phenol hot belt system are collected and are fed through line 101 and stored in a phenol accumulator drum 102 at about 275 F. and about 25 p.s.i.g.

The thus refined feed can be dewaxed and/ or hydrofined or sent to storage.

FIG. 3 is a schematic flow diagram of the phenol hot belt system. The combined overheads from the raffinate and extract recovery towers of the phenol treating plant are introduced to the hot belt system through line 83 at about 430 F. and at about 50 p.s.i.g. The phenol hot belt exchangers are in parallel to minimize the pressure drop between the phenol recovery towers 27 and 37 and the phenol accumulator drum 102 (FIG. 2). The hot phenol vapors are distributed through line 84 and are collected in line 98 after passing through the various heat exchangers, E-l through E-5. The hot belt system consists of five heat exchangers, E-l through -5, and a phenol bypass line 86.

The heat exchangers provide the following services:

Heat exchanger E-l receives hot phenol vapors through 8) line and discharges them through line and the cooled and condensed phenol vapor is collected in line 98. In cooling the hot phenol vapor through heat exchanger E-l, the feed to phenol extract recovery tower 27 is heated from about 180 F. to about 400 F., prior to entering extract furnace E-7.

Heat exchanger E3 receives hot phenol vapor through line 87; cooled phenol vapor is removed through line 96. The feed to the phenol raflinate recovery tower is heated in exchanger E3 from about 200 to about 400 F. prior to entry into raffinate furnace E-8.

Heat exchangers E-2 and 13-5 receive hot phenol vapor through line 88 which splits into lines 90 and 92. Line 90 provides the hot phenol vapor for heat exchanger E2 wherein slack wax/ propane solution is heated from about F. to about 320 F. The cooled phenol vapor leaves through line 91.

Heat exchanger E-S receives hot phenol vapor through line 92 and heats dewaxed oil propane solution from about 140 F. to about 340 F. The cooled phenol vapors are withdrawn through line 93 and are combined in line 94 with the cooled phenol vapor from line 91.

Heat exchanger E-4 receives hot phenol vapor through line 89 and heats deasphalted oil/propane solution from about F. to about 360 F. The cooled phenol vapors are removed from exchanger E-4 by line 97.

When the phenol plant is running at low circulation rates, makeup phenol is sent to the hot belt by injecting phenol into the phenol extract stream prior to its entry into the phenol extract furnace E-7. This insures that enough heat is available in the hot phenol vapor to flash propane from the deasphalted oil, dewaxed oil, and slack wax solutions in the high pressure flash drums. In the event that excess heat is available in the phenol hot belt system, part of the hot phenol bypasses the heat exchangers via line 86. Condensed phenol vapors are collected from the various heat services and the bypass line, and pass into line 98 and are fed through line 99 into hot belt trim cooler 100 wherein the temperature of the condensed phenol is reduced to about 275 F. and fed through line 101 to the phenol accumulator drum 102 (see FIG. 2).

It is obvious from the above description of the invention that substantial savings have been made by cooling the hot phenol vapors by heat exchange with cool dewaxing and deasphalting process streams and by concomitantly heating the latter streams to remove propane solvent.

It is to be understood that the specific temperatures and pressures at which the various process steps have been carried out can be varied within temperature and pressure ranges of such steps known to those skilled in the art or that would be obvious to those skilled in the art without departing from the claimed invention. The specific temperatures and pressures are recited only as illustrative and not to limit the invention in any way.

What is claimed is:

1. An improved process for refining lubricating oil fractions and for vaporizing, condensing and recovering vaporizable solvents used in conjunction with said refining process which comprises in combination (a) a propane deasphalting step, a phenol extraction step, and a propane dewaxing step, wherein (b) the phenol extract and nonaromatic phenol raflinate phases from the phenol extraction step are separately heated to a temperature at which hot phenol vapors are selectively removed and combined, cooled and condensed; and wherein (c) a deasphalted oil/ propane phase and the asphalt/ propane phase are separated by the propane deasphalting step, and a dewaxed oil/propane phase, and the slack wax/ propane phase are separated by the propane dewaxing step, and

(d) propane is removed from the respective separated 9 phases by heating the separated phase and flashing the propane from the respective phases,

(e) the improvement which comprises cooling and condensing the hot phenol vapors by indirect heat transfer between the hot phenol vapors and the rela tively cool deasphalted oil/propane phase, the de- Waxed oil/propane phase and the slack Wax/propane phase, simultaneously heating said phases and vaporizing the propane therefrom (f) separating, condensing and collecting the vaporized propane and collecting said condensed phenol.

2. Process of claim 1 wherein the propane separated from the respective deasphalted oil/solvent phases, asphalt/ solvent phase, dewaxed oil/ solvent phase and slack Wax/solvent phase is combined, cooled, condensed, compressed and collected in a common propane solvent system.

References Cited by the Examiner UNITED STATES PATENTS Gard 208-34 Kleiber l96134 Kuhl 196134 Crittenden 208-83 Bray 20834 Dickinson 196-134 Johnston et al. 2()834 Smith 196134 Porter et al. 208-34 Gilmore 208361 5 DELBERT E. GANTZ, Primary Examiner. ALPHONSO D. SULLIVAN, Examiner.

H. LEVINE, Assistant Examiner. 

1. AN IMPROVED PROCESS FOR REFINING LUBRICATING OIL FRACTIONS AND FOR VAPORIZING, CONDENSING AND RECOVERING VAPORIZABLE SOLVENTS USED INCONJUNCTION WITH SAID REFINING PROCESS WHICH COMPRISES INCOMBINATION(A) A PROPANE DEASPHALTING STEP, A PHENOL EXTRACTION STEP, AND A PROPANE DEWAXING STEP, WHEREIN (B) THE PHENOL EXTRACT AND NONAROMATIC PHENOL RAFFINATE PHASES FROM THE PHENOL EXTRACTION STEP ARE SEPARATELY HEATED TO A TEMPERATURE AT WHICH HOT PHENOL VAPORS ARE SELECTIVELY REMOVED AND COMBINED, COOLED AND CONDENSED; AND WHEREIN (C) A DEASPHALTED OIL/PROPANE PHASE AND THE ASPHALT/ PROPANE PHASE ARE SEPARATED BY THE PROPANE DEASPHALTING STEP, AND A DEWAXED OIL/PROPANE PHASE, AND THE SLACK WAX/PROPANE PHASE ARE SEPARATED BY THE PROPANE DEWAXING STEP, AND (D) PROPANE IS REMOVED FOM THE RESPECTIVE SEPARATE PHASES BY HEATING THESEPARATED PHASE AND FLASHING THE PROPANE FROM THE RESPECTIVE PHASES, (E) THE IMPROVEMENT WHICH COMPRISES COOLING AND CONDENSING THE HOT PHENOL VAPORS BY INDIRECT HEAT TRANSFER BETWEEN THE HOT PHENOL VAPORS AND THE RELATIVELY COOL DEASPHALTED OIL/PROPANE PHASE, THE DEWAXED OIL/PROPANE PHASE AND THE SLACK WAX/PROPANE PHASE, SIMULTANEOUSLY HEATING SAID PHASES AND VAPORIZING THE PROPANE THEREFROM(F) SEPARATING, CONDENSING AND COLLECTING THE VAPORIZED PROPANE AND COLLECTING SAID CONDENSED PHENOL. 